Sensitive polar relay



April 7, 1936. w. v. JOHNSON SENSITIVE POLAR RELAY Filed Jul 10, 1954 WITNESSES:

INVENTOR We /7o/7 l/Jfinson.

ORNEY Patented Apr. 7, 1936 UNITED STTES FICE 2&35377 SENSITIVE roman. RELAY of Pennsylvania Application July ll ll, 1934, Serial No. 734,517

5 Claims.

My invention relates to relays of the type in which an armature of magnetic material is subject to the influence of a permanent magnet, particularly to such relays of the polar type for use in connection with direct current apparatus.

In one form of such relays known to the prior art, a reed of magnetic material is rigidly fastened at one end in such manner that it normally lies midway between the poles of a permanent magnet, but may be flexed toward one or the other pole depending upon the direction of energization of the relay Winding. In this arrangement, upon deflection of the reed from its central position, the reed develops a centering force approximately proportional to its deflection, in the same manner as a spring, and the nearest pole of the permanent magnet develops a force of attraction which depends upon the deflection but which varies as a higher power than unity of the deflection. In order to secure mechanical stability of the reed, it is necessary that the centering force exceed the magnetic force at all positions of the reed. This requires a reed of such stiffness that a high degree of relay sensitivity cannot be secured,

It is an object of my invention to provide a novel relay of the form indicated above, in which a very light reed may be used, and. mechanical stability may be maintained throughout the range of travel of the reed.

Other objects of my invention will become evident from the following detailed description taken in conjunction with the accompanying drawing, in which the single figure is a diagrammatic view of a relay embodying my invention.

Referring to the figure in detail, a U-shaped permanent magnet l is, provided with a central core member 2 of any suitable magnetic material, and with a pair of pole tip members 3 of soft iron or laminated steel. The core member 2 and the pole tip members 3 may be secured to the permanent magnet I by any suitable means, such as machine screws (not shown). The core member 2 is provided with a relay winding 4, and is slotted at its upper end to receive a flexible reed 5 of magnetic material. A pair of cams t are provided for varying the effective free length of the reed ,5 in response to deflections in the reed. The cams 6 are of slightly curved contour and are secured .in contact with the reed 5 at its fixed end, by any suitable means such as the (Cl. ENE-=93) the latter is in its central position and decreases upon movement of the latter toward each side to an extent sufficient to approximately compensate for the increase of magnetic attraction occasioned by movement of the reed 5 toward one or the other of the pole tips That is to say, in the absence of the cam 6, the biasing force developed by the reed 5 upon movement away from its central position would be a linear function of the deflection, whereas the force of attraction developed by the nearest pole tip 3 for the reed 5 would approximate a function of the deflection of a higher exponent than unity. However, because of the cam t, the increase of magnetic attraction is approximately compensated for, so that the reed 5 becomes substantially stable in any position in which it may assume the air gap between the pole tip A pair of movable contact members 8 are secured to the free end of the reed 5 for engagement with suitable adjustable stationary contact mem bers 9.

The operation of the relay will be obvious from the above description. Assuming the reed 5 to be in its normal central position and the relay coil 4 to be deenergized, if a current flows in the coil 4, the free end of the reed 5 will become magnetized with a polarity depending upon the direction of current flow in the coil 4. The reed 5 will then move so that one of the movable contact members 8 engages one of the stationary contact members 9 depending upon the direction of current flow. As the reed 5 is quite flexible, and the force necessary to bend the reed is ap-- proximately equal to the magnetic force developed because of the deflection of the reed, the energy required to effect operation of the relay is quite low.

I do not intend that the present invention shall be restricted to the specific structural details, arrangement of parts or circuit connections herein set forth, as various modifications thereof may be efiected without departing from the spirit and scope of my invention. I desire, therefore, only such limitations shall be imposed as are indicated in the appended claims.

I claim as my'invention:

1. In a relay, a magnetic structure, contact operating means including a movable member subject to an operating force dependent upon .a magnetic condition produced by said structure and upon the position of said movable member, said mechanism including a resilient element for exerting a biasing force modifying'said operating force, and a cam mounted in contact with said resilient element, said cam having a contour departing slightly from that of said resilient element and being arranged to change the effective free length of said resilient element.

2. In a relay, a permanent magnet having a pole tip, contact operating mechanism including magnetic means subject to a magnetic force dependent upon the field of said pole tip, said mechanism including a resilient element for exerting a biasing force in opposition to said magnetic force, and a cam mounted in contact with said resilient element, said cam having a contour departing slightly from that of said resilient element, and being arranged to change the effective free length of said resilient element.

3. In a relay, a permanent magnet having a pair of pole tips, contact operating mechanism including magnetic means subject to a magnetic force dependent upon the field between said pole tips, said mechanism including resilient centering means, and cam means arranged to modify the action of said centering means to increase the mechanical stability of said contact operating mechanism.

4. In a relay, a permanent magnet having a of pole tips, contact operating mechanism including magnetic means subject to a magnetic force dependent upon the field between said pole tips and operable through a range of positions including a center position, said mechanism including a resilient reed effective to exert a biasing force acting toward said center position, and a pair of cams mounted in contact with said reed, said cams having contours departing slightly from the adjacent contours of said reed and being arranged to modify said biasing force to increase the mechanical stability of said contact operating mechanism.

5. In a polarized relay, a permanent magnet having a pair of pole tips, a magnetic reed mounted for resilient movement through a range of positions between said pole tips including a center position, a polarizing coil inductively associated with said reed, and a pair of cams mounted in contact with said reed, said cams having contours departing slightly from the adjacent contours of said reed and being arranged to modify the centering force developed by said reed to approximately compensate for the variation of magnetic attraction of said pole tips for said reed in various positions of the latter.

WELTON V. JOHNSON. 

